LIN Communication Formats
1266
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Serial Communication Interface (SCI)/ Local Interconnect Network (LIN)
Module
25.7.11
Transmit Buffers
To reduce the CPU load when transmitting a LIN N-byte (with N = 1–8) response in interrupt mode or
DMA mode, the SCI/LIN module has eight transmit buffers, TD0–TD7 in LINTD0 and LINTD1. With these
transmit buffers, an entire LIN response field can be preloaded in the TXy transmit buffers. Optionally, a
DMA transfer could be done on a byte-per-byte basis when multi-buffer mode is not enabled (MBUF
MODE bit in the SCIGCR1 register).
The multi-buffer 3-bit counter counts the data bytes transferred from the TDy transmit buffers register if
multi-buffer mode is enabled, or from TD0 to SCITXSHF if multi-buffer mode is disabled. The 3-bit
compare register contains the number of data bytes expected to be transmitted. If the ID field is not used
to convey message length (see
Note: Optional Control Length Bits
in
), the LENGTH value
indicates the expected length and is used instead to load the 3-bit compare register. Whether the length
control field or the LENGTH value is used is selectable with the COMM MODE bit.
A transmit interrupt (TX interrupt), and a transmit ready flag (TXRDY flag), and a DMA request (TXDMA)
could occur after transmitting a response. A DMA request can be generated for each transmitted byte or
for the entire response depending on whether multi-buffer mode is enabled or not (MBUF MODE bit in the
SCIGCR1 register).
illustrates the transmit buffers.
The checksum byte will be automatically generated by the checksum calculator and sent after the data-
fields transmission is finished. The multi-buffer 3-bit counter counts the data bytes transferred from the
TDy buffers into the SCITXSHF register.
NOTE:
The transmit interrupt request can be eliminated until the next series of data is written into
the transmit buffers LINTD0 and LINTD1, by disabling the corresponding interrupt via the
SCICLRINT register or by disabling the transmitter via the TXENA bit.